Fuel injector

ABSTRACT

A fuel injection valve includes: a swirl chamber having an inner peripheral wall formed to be gradually increased in curvature toward a downstream side from an upstream side; a swirl passage, through which a fuel is introduced into the swirl chamber; and a fuel injection port opened to the swirl chamber, wherein the swirl chamber and the swirl passage are formed so that a side wall of the swirl passage connected to a downstream end side of the swirl chamber, or an extension thereof is made not to intersect a downstream side portion of the inner peripheral wall of the swirl chamber, or an extension thereof.

BACKGROUND OF THE INVENTION

The present invention relates to a fuel injection valve used in internalcombustion engines to inject a swirling fuel to enable achieving animprovement in atomizing performance.

A fuel injection valve described in JP-A-2003-336562 is known as priorart, in which a swirling flow is made use of to accelerate atomizationof a fuel injected from a plurality of fuel injection ports.

In this fuel injection valve, a lateral passage in communication with adownstream end of a valve seat and a swirl chamber into which adownstream end of the lateral passage is opened tangentially are formedbetween a valve seat member, to a front end surface of which adownstream end of the valve seat cooperating with a valve body isopened, and an injector plate joined to the front end surface of thevalve seat member, and a fuel injection port, from which a fuel givenswirl in the swirl chamber is injected is formed in the injection plate,and the fuel injection port is arranged offset a predetermined distancetoward an upstream end of the lateral passage from a center of the swirlchamber.

Also, in this fuel injection valve, an inner peripheral surface of theswirl chamber is decreased in radius of curvature toward a downstreamside from an upstream side in a direction along the inner peripheralsurface of the swirl chamber. That is, the curvature is increased towardthe downstream side from the upstream side in the direction along theinner peripheral surface of the swirl chamber. Also, the innerperipheral surface of the swirl chamber is formed along an involutecurve having a basic circle in the swirl chamber.

Such construction enables effectively accelerating atomization of a fuelfrom respective fuel injection ports.

In order to inject a swirling fuel, which is symmetric (uniform) inswirl intensity in a circumferential direction, from a fuel injectionport, it is necessary to contrive a flow passage configuration includingthe shape of a swirl chamber and a lateral passage (swirl passage) inorder to make a swirling flow symmetrical at an outlet of the fuelinjection port.

In the prior art described in JP-A-2003-336562, one (a side wallconnected to an upstream end of an inner peripheral surface of a swirlchamber in a fuel swirling direction) of side walls, which define alateral passage, is connected tangentially to the inner peripheralsurface of the swirl chamber and the other (a side wall connected to adownstream end of the inner peripheral surface of the swirl chamber inthe fuel swirling direction) of the side walls is provided in a mannerto intersect the inner peripheral surface of the swirl chamber.Therefore, a connection of both walls, on which the other of the sidewalls and the inner peripheral surface of the swirl chamber intersecteach other, is shaped to be sharp at the point like a knife edge.

With such connection, when the side wall of the lateral passage or theinner peripheral surface of the swirl chamber is minutely dislocated,the connection of both walls is liable to be dislocated. Suchdislocation of the connection is responsible for generation of steepdrift toward a fuel injection port, so that it is possible that aswirling flow is damaged in symmetric property (uniformity).

SUMMARY OF THE INVENTION

The invention has been thought of in view of the circumstances describedabove and has its object to provide a fuel injection valve, which isheightened in uniformity in a circumferential direction of a swirlingflow.

In order to attain the above object, the invention provides a fuelinjection valve including a swirl chamber having an inner peripheralwall formed to be gradually increased in curvature toward a downstreamside from an upstream side, a swirl passage, through which a fuel isintroduced into the swirl chamber, and a fuel injection port opened tothe swirl chamber, wherein the swirl chamber and the swirl passage areformed so that a side wall of the swirl passage connected to adownstream end side of the swirl chamber, or an extension thereof ismade not to intersect a downstream side portion of the inner peripheralwall of the swirl chamber, or an extension thereof.

At this time, assuming, respectively, a first straight line segmentconnecting between a center of the swirl chamber and a starting point ofthe inner peripheral wall of the swirl chamber on an upstream side, afirst point Y0, at which the first line segment and an extension of theinner peripheral wall extended toward a downstream side intersect eachother, a second straight line segment passing through the first point Y0and being perpendicular to the first line segment, a second point P0, atwhich the second line segment intersects the inner peripheral wall or anextension thereof on an upstream side of the first point Y0, a thirdstraight line segment connecting between the second point P0 and thecenter of the swirl chamber, a third point, at which the side wall ofthe swirl passage and the third line segment intersect each other, afourth straight line segment being parallel to the second line segmentand being in contact with the inner peripheral wall or an extensionthereof between the first point and the second point, and a fourthpoint, at which the fourth line segment intersects the third linesegment, it is preferable that the third point is positioned on thethird line segment on a side more distant from the center of the swirlchamber than the fourth point.

Also, it is preferable that the cross section of the swirl chamber isdefined by an involute curve or a spiral curve.

Also, it is preferable that a thickness forming portion is formedbetween a downstream end of the side wall of the swirl passage and adownstream end of the inner peripheral wall of the swirl chamber.

Also, it is preferable that the cross section of the thickness formingportion is defined by a circular-shaped portion.

Also, it is preferable that the circular-shaped portion is formed to bein contact with the inner peripheral wall and the side wall at thedownstream end of the inner peripheral wall and the downstream end ofthe side wall.

Also, in order to attain the above object, the invention provides a fuelinjection valve including a swirl chamber having an inner peripheralwall formed to be gradually increased in curvature toward a downstreamside from an upstream side, a swirl passage, through which a fuel isintroduced into the swirl chamber, and a fuel injection port opened tothe swirl chamber, wherein a thickness forming portion is formed betweena downstream end of a side wall of the swirl passage connected to adownstream end side of the swirl chamber and a downstream end of theinner peripheral wall of the swirl chamber.

It is preferable that the cross section of the thickness forming portionis defined by a circular-shaped portion.

It is preferable that the circular-shaped portion is formed to be incontact with the inner peripheral wall and the side wall at thedownstream end of the inner peripheral wall and the downstream end ofthe side wall.

According to the invention, the connection of the swirl chamber and theswirl passage, that is, a portion, at which a fuel inflowing from theswirl passage and a fuel orbiting in the swirl chamber merge together,can be heightened in positional accuracy, flow at the merging portion issmoothly formed, and a stable swirling flow being high in uniformity ina circumferential direction can be generated. Other objects, features,and advantages of the invention will become apparent from the followingdescription of an embodiment of the invention when taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal section showing the whole configuration of afuel injection valve, according to the invention, in cross section alonga valve axis.

FIG. 2 is a longitudinal section showing the neighborhood of a nozzlebody in the fuel injection valve according to the invention.

FIG. 3 is a plan view of an orifice plate positioned at a lower end ofthe nozzle body in the fuel injection valve according to the invention.

FIG. 4 is a plan view illustrating the relationship among a swirlchamber, a swirl passage, and a fuel injection port in the fuelinjection valve according to the invention.

FIG. 5 is a cross sectional view taken along the line V-V in FIG. 4 andillustrating the relationship among the swirl chamber, the swirl passageand the fuel injection port.

FIG. 6 is a view illustrating the relationship between the thickness ofa thickness forming portion and an error in symmetric property of spray.

FIG. 7 is a plan view showing an example, in which a connection of theswirl chamber and the swirl passage is edged to be sharp at the pointlike a knife edge.

FIG. 8A is a plan view illustrating, in detail, the structure of thethickness forming portion in the fuel injection valve according to theinvention.

FIG. 8B is a view showing, in enlarged scale, an A-part in FIG. 8A.

FIG. 9 is a plan view illustrating the relationship among the swirlchamber, the swirl passage and the fuel injection port when the swirlpassage is tapered.

FIG. 10A is a view showing flow in the structure shown in FIG. 7.

FIG. 10B is a view showing flow in the structure shown in FIG. 8A.

DESCRIPTION OF THE EMBODIMENTS

An embodiment of the invention will be described hereinafter withreference to FIGS. 1 to 7.

Referring to FIGS. 1 to 3, a fuel injection valve 1 comprises a magneticyoke 6 surrounding an electromagnetic coil 9, a core 7 positionedcentrally of the electromagnetic coil 9 and in contact at one endthereof with the yoke 6, a valve body 3, which lifts a predeterminedamount, a valve seat surface 10 brought into contact with the valve body3, a fuel injection chamber 2, which permits passage of a fuel flowingthrough a clearance between the valve body 3 and the valve seat surface10, and an orifice plate 20 having a plurality of fuel injection ports23 a, 23 b, 23 c disposed downstream of the fuel injection chamber 2.

Provided centrally of the core 7 is a spring 8, which pushes the valvebody 3 against the valve seat surface 10.

In a state, in which the coil 9 is not energized, the valve body 3 andthe valve seat surface 10 come into closely contact with each other. Inthis state, since a fuel passage is closed, a fuel remains in the fuelinjection valve 1 and fuel injection is not performed from each of thefuel injection ports 23 a, 23 b, 23 c provided in plural.

When the coil 9 is energized, the valve body 3 is moved by anelectromagnetic force until it abuts against a lower end surface of thecore 7 opposed to the valve body 3.

In this valve opened state, since a clearance is formed between thevalve body 3 and the valve seat surface 10, the fuel passage is openedto permit a fuel to be injected from the plurality of fuel injectionports 23 a, 23 b, 23 c.

The fuel injection valve 1A is formed with a fuel passage 5 having afuel inlet 5 a, and the fuel passage 5 is one, which includes athrough-hole portion extending through the center of the core 7 andthrough which a fuel pressurized by a fuel pump (not shown) is led tothe fuel injection ports 23 a, 23 b, 23 c through an interior of thefuel injection valve 1.

As described above, as the coil 9 is energized (injection pulse), thefuel injection valve 1 switches the position of the valve body 3 betweena valve opened state and a valve closed state to control a fuel feedrate. The valve body is designed to eliminate fuel leakage in the valveclosed state.

In fuel injection valves of this kind, balls (steel balls for ballbearings on JIS Standards), which are high in roundness and subjected tomirror finish, are used for the valve body 3 to be beneficial to animprovement in seating quality.

On the other hand, the valve seat angle of the valve seat surface 10,with which the ball comes into close contact, is from 80° to 100°, whichis optimum to provide for a favorable abrasive quality and to enablemaintaining the ball seat quality very high.

In addition, a nozzle body 4 having the valve seat surface 10 isheightened in hardness by means of hardening and also relieved ofuseless magnetism by means of demagnetizing treatment.

Such structure of the valve body 3 enables injection quantity controlwithout fuel leakage. Therefore, the valve body structure is madeexcellent in cost performance.

As shown in FIG. 2, the orifice plate 20 has its upper surface 20 a incontact with a lower surface 4 a of the nozzle body 4 and an outerperiphery of the contact portion is subjected to laser welding to befixed to the nozzle body 4.

In addition, a vertical direction described in the specification andclaims of the present application is based on FIG. 1 such that the fuelinlet 5 a is on an upper side and the fuel injection ports 23 a, 23 b,23 c are on a lower side in a direction along a valve axis 1 c of thefuel injection valve 1.

Provided at a lower end of the nozzle body 4 is a fuel introducing port11 having a smaller diameter than the diameter φS of a seat portion 10 aof the valve seat surface 10. The valve seat surface 10 isconical-shaped to be formed centrally of a downstream end thereof withthe fuel introducing port 11. The valve seat surface 10 and the fuelintroducing port 11 are formed so that a center line of the valve seatsurface 10 and a center line of the fuel introducing port 11 agree withthe valve axis 1 c. The fuel introducing port 11 forms that opening onthe lower end surface 4 a of the nozzle body 4, which is communicated toa central hole (central port) 24 of the orifice plate 20.

The central hole 24 is a concave-shaped portion provided on the uppersurface 20 a of the orifice plate 20, swirl passages 21 a, 21 b, 21 cextend radially from the central hole 24, and upstream ends of the swirlpassages 21 a, 21 b, 21 c are opened to an inner peripheral surface ofthe central hole 24 to be communicated to the central hole 24.

A downstream end of the swirl passage 21 a is connected to a swirlchamber 22 a, a downstream end of the swirl passage 21 b is connected toa swirl chamber 22 b, and a downstream end of the swirl passage 21 c isconnected to a swirl chamber 22 c. The swirl passages 21 a, 21 b, 21 cserve as fuel passages, through which a fuel is supplied to the swirlchambers 22 a, 22 b, 22 c, respectively, and in this sense, the swirlpassages 21 a, 21 b, 21 c may be called swirling fuel supply passages.

Wall surfaces of the swirl chambers 22 a, 22 b, 22 c are formed to begradually increased in curvature toward a downstream side from anupstream side (gradually decreased in radius of curvature). In thisrespect, the curvature may be continuously increased, or stepwisegradually increased toward a downstream side from an upstream side whilethe curvature is made constant in a predetermined range. A typicalexample of a curve continuously increased in curvature toward adownstream side from an upstream side includes an involute curve(configuration), or a spiral curve (configuration). While the embodimenthas been described with respect to a spiral curve, the explanation isapplicable even when an involute curve is adopted assuming that thecurvature is gradually increased toward a downstream side from anupstream side.

The fuel injection ports 23 a, 23 b, 23 c, respectively, are openedcentrally of the swirl chambers 22 a, 22 b, 22 c.

Both the nozzle body 4 and the orifice plate 20 are formed so thatpositioning thereof is simply and readily carried out, and heightened indimensional accuracy at the time of assembling.

The orifice plate 20 is manufactured by means of press-forming (plasticworking), which is advantageous in mass-productiveness. In addition,other methods, such as electrical discharge machining, electroforming,etching working, etc., in which stress is not applied comparatively andwhich are high in machining accuracy, than the above method areconceivable.

Subsequently, the structure of the orifice plate 20 will be described indetail with reference to FIGS. 3 to 7.

Referring to FIG. 3, the orifice plate 20 is formed with the centralhole 24 communicated to the fuel introducing port 11, and the centralhole 24 is connected to the three swirl passages 21 a, 21 b, 21 carranged at regular intervals (intervals of 120 degrees) in acircumferential direction of the central hole and extended radiallytoward an outer peripheral side in a diametrical direction.

Referring to FIGS. 4 and 5, one 21 a of the swirl passages is openedtangentially of the swirl chamber 22 a and the fuel injection port 23 ais opened centrally of the swirl chamber 22 a. In addition, according tothe embodiment, an inner peripheral wall of the swirl chamber 22 a isformed to draw a spiral curve on a plane (section) perpendicular to thevalve axis 1 c, that is, spiral-shaped so that a vortical center of thespiral curve and a center of the fuel injection port 23 a agree witheach other. In the case where the swirl chamber 22 a is defined by aninvolute curve, it is formed so that a center of a basic circle of theinvolute curve and the center of the fuel injection port 23 a agree witheach other. However, the center of the fuel injection port 23 a may bearranged offset from the vortical center of the spiral curve and thecenter of the basic circle of the involute curve.

The spiral shape of the swirl chamber is formed so that a radius R ofthe spiral curve meets the relationships represented by the formulae (1)and (2).R=D/2×(1−a×θ)  (1)a=W*/(D/2)/(2π)  (2)

Here, D indicates a diameter of a basic circle, W* indicates a width ofa swirl passage, and W* in the invention is a numeric value including athickness φK (shown in FIGS. 4 and 5).

An inner peripheral surface of the swirl chamber 22 a includes astarting end (upstream end) Ssa and a terminating end (downstream end)Sea. One 21 as of side walls of the swirl passage 21 a is connectedtangentially to the starting end (starting point) Ssa. Provided at theterminating end (terminating point) Sea is a circular-shaped portion 26a formed to come into contact with the spiral curve at the terminatingpoint Sea. Since the circular-shaped portion 26 a is formed over thewhole of the swirl passage 21 a and the swirl chamber 22 a in aheightwise direction (direction along a swirl central axis), it definesa partial cylindrical-shaped portion formed in a predetermined angularrange in a circumferential direction. The other 21 ae of the side wallsof the swirl passage 21 a is formed to come into contact with acylindrical-shaped surface defined by the circular-shaped portion 26 a.

The cylindrical-shaped surface defined by the circular-shaped portion 26a defines a connecting surface (intermediate surface) connecting betweena downstream end of the side wall 21 ae of the swirl passage 21 a andthe terminating end Sea of the inner peripheral surface of the swirlchamber 22 a. Also, owing to the provision of the connecting surface 26a, it is possible to provide a thickness forming portion 25 a on aconnection of the swirl chamber 22 a and the swirl passage 21 a, thusenabling connecting the swirl chamber 22 a and the swirl passage 21 awith a wall surface, which has a predetermined thickness, therebetween.In other words, a configuration, which is sharp at the point like aknife edge, is not formed on the connection of the swirl chamber 22 aand the swirl passage 21 a.

A connection of the side wall 21 ae of the swirl passage 21 a and theswirl chamber 22 a will be described later in detail.

The fuel injection ports 23 a, 23 b, 23 c are opened in a direction (afuel outflow direction, a direction along a central axis), which isparallel to the valve axis 1 c of the fuel injection valve 1 anddownward in the embodiment, but may be inclined at a desired directionrelative to the valve axis 1 c to diffuse sprays (make respective spraysdistant from one another to restrict interference).

As shown in FIG. 5, that cross sectional shape of the swirl passage 21a, which is perpendicular to a flow direction, is a rectangle(rectangular shape) and designed to measure a dimension, which isadvantageous to press-forming. In particular, workability is madeadvantageous by making a height HS of the swirl passage 21 a small ascompared with a width W.

Since the rectangular portion constitutes a throttle (minimum crosssectional area), design is accomplished so as to enable neglecting thatpressure loss, which is caused until a fuel flowing into the swirlpassage 21 a reaches the swirl passage 21 a through the fuel injectionchamber 2, the fuel introducing port 11, and the central hole 24 of theorifice plate 20 from the seat portion 10 a of the valve seat surface10.

In particular, the fuel introducing port 11 and the central hole 24 ofthe orifice plate 20 are designed to define a fuel passage of a desireddimension so as not to cause a pressure loss due to a sharp bend.

Accordingly, pressure energy of a fuel is efficiently converted at theswirl passage 21 a into swirl speed energy.

Flow accelerated at the rectangular portion is led to the fuel injectionport 23 a on the downstream side while maintaining adequate swirlintensity, that is, so-called swirl speed energy.

Swirl intensity (swirl number S) of a fuel is represented by the formula(3).S=d·LS/n·ds ²  (3)ds=2·W·HS/(W+HS)  (4)

Here, d indicates a diameter of a fuel injection port, LS indicates adistance between the center line of the swirl passage W and a center ofthe swirl chamber DS, and n indicates the number of swirl passages, onein the embodiment.

Also, ds indicates a hydraulic diameter converted from a swirl passageand is represented by the formula (4), W indicates a width of a swirlpassage, and HS indicates a height of a swirl passage.

The diameter DS of the swirl chamber 22 a is determined so thatinfluences of friction loss caused by a fuel flow and of friction losson a chamber wall are made as small as possible.

The dimension about four to six times a hydraulic diameter ds is made anoptimum value, and this method is applied in the embodiment.

As described above, in the embodiment, the thickness forming portion 25a is formed on the connection of a downstream end of the innerperipheral wall of the swirl chamber 22 a and the swirl passage 21 a tohave a predetermined thickness φK.

Since the relationship among the swirl passage 21 b, the swirl chamber22 b and the fuel injection port 23 b and the relationship among theswirl passage 21 c, the swirl chamber 22 c and the fuel injection port23 c are the same as the relationship among the swirl passage 21 a, theswirl chamber 22 a and the fuel injection port 23 a, an explanationtherefore is omitted.

In addition, while fuel passages comprising a combination of the swirlpassage 21, the swirl chamber 22 and the fuel injection port 23 areprovided in three sets according to the embodiment, they may be furtherincreased to heighten the configuration of spray and variations ofinjection quantity in degree of freedom. Also, fuel passages comprisinga combination of the swirl passage 21, the swirl chamber 22 and the fuelinjection port 23 may be provided in two sets, or one set.

Since a fuel passage comprising a combination of the swirl passage 21 a,the swirl chamber 22 a and the fuel injection port 23 a, a fuel passagecomprising a combination of the swirl passage 21 b, the swirl chamber 22b and the fuel injection port 23 b, and a fuel passage comprising acombination of the swirl passage 21 c, the swirl chamber 22 c and thefuel injection port 23 c are structured in the same manner, therespective fuel passages are not distinguished in the followingdescriptions but described simply as the swirl passage 21, the swirlchamber 22 and the fuel injection port 23.

The action and function of the thickness forming portion 25 a will bedescribed with reference to FIGS. 6 to 9. FIG. 6 is a view illustratingthe relationship between the thickness of the thickness forming portion25 a and an error in symmetric property of spray. FIG. 7 is a plan viewshowing an example, in which a connection PO of the swirl chamber 22 aand the swirl passage 21 a is edged (thickness of less than 0.01 mm) tobe sharp at the point like a knife edge. FIG. 8A is a plan viewillustrating the structure of the thickness forming portion 25 indetail. FIG. 9 is a plan view illustrating a difference of flow betweenthe structure in FIG. 7 and the structure in FIG. 8A.

FIG. 7 shows an example, in which the side wall 21 e of the swirlpassage 21 and the inner peripheral wall of the swirl chamber 22intersect each other. The side wall 21 e and the inner peripheral wallof the swirl chamber 22 intersect each other whereby an edge-shapedportion being sharp at the point like a knife edge is formed on theconnection PO. The current processing technique makes it possible tomake the thickness of the edge-shaped portion less than 0.01 mm.

The connection PO is a point of intersection, at which a spiral curvedrawn by the inner peripheral wall of the swirl chamber 22 intersects aline extended perpendicular from a position YO at which the spiral curvedrawn by the inner peripheral wall of the swirl chamber 22 intersectsthe Y axis, and a portion of the extended line on the left of PO definesthe side wall 21 e of the swirl passage 21.

A point P1 indicates a position of a connection in the case where theswirl passage 21 is manufactured to be large in width and in the casewhere a side wall is provided in a position 39. In such case, acollision angle of a fuel orbiting in the swirl chamber 22 and a fuelfrom the swirl passage 21 increases, so that an asymmetric swirling flowis fed to the fuel injection port 23.

Also, since the fuel injection port 23 is seen well from the swirlpassage 21, a fuel inflowing from the swirl passage 21 becomes easy toflow steeply toward the fuel injection port 23 and so an asymmetricswirling flow is fed.

Since the thickness forming portion 25 having a predetermined thicknessφK is provided on the connection, shown in FIG. 4, of the swirl chamber22 a and the swirl passage 21 a, the symmetric property of spray can bemade to assume a design target value as shown in FIG. 6.

The thickness forming portion 25 defines a wall surface having an origincorresponding to the point PO shown in FIG. 8A and is formed as a wallsurface 26 drawing that circle of an optional diameter, whichcircumscribes the spiral curve of the swirl chamber 22 at the point PO.

Referring to FIG. 8, the structure of the thickness forming portion 25will be described in detail.

An extension of the side wall 21 e (the wall surface in a heightwisedirection) of the swirl passage 21 does not intersect an extension of aspiral curve 22 s, which is drawn by the inner peripheral wall of theswirl chamber 22, in an angular range of more than 180 degrees rotated(orbited) from the starting point Ss of the spiral curve 22 s. Thereby,a substantial thickness can be formed between the side wall 21 e and thespiral curve 22 s drawn by the inner peripheral wall of the swirlchamber 22.

A side wall 21 s of the swirl passage 21 is formed in a manner to comeinto contact with a basic circle 30 at the point Ss. The basic circle 30has its center O₃₀ agreeing with a center O_(22S) of a spiral and hasits radius R equal to a distance between the starting point Ss of thespiral curve 22 s and the center O_(22S) of the spiral. The center O₃₀of the basic circle 30 and the center O_(22S) of the spiral define acenter of the swirl chamber. Also, the point Ss makes a starting pointof the spiral curve 22 s of the inner peripheral wall of the swirlchamber 22. Accordingly, the side wall 21 s constitutes a side wallconnected to an upstream side end of the spiral curve 22 s drawn by theinner peripheral wall of the swirl chamber 22.

A first line segment (straight line) 31 connecting between the centerO₃₀ (the center O_(22S) of the spiral) of the basic circle 30 and thestarting point Ss in an angular position rotated (orbited) 360 degreesfrom the starting point Ss is assumed. A first point Y0, at which thefirst line segment 31 and an extension of the spiral curve 22 sintersect each other, is assumed. A second line segment (straight line)32 passing through the first point Y0 and being perpendicular to thefirst line segment 31 is assumed. A second point P0, at which the secondline segment 32 intersects the spiral curve 22 s (or an extensionthereof) on an upstream side of the first point Y0, is assumed. A thirdline segment (straight line) 33 connecting between the second point P0and the center O_(22S) of the spiral (the center O₃₀ of the basic circle30) is assumed. A third point 34, at which the side wall 21 e and thethird line segment 33 intersect each other, is assumed. A fourth linesegment (straight line) 35 being parallel to the second line segment 32and in contact with an extension of the spiral curve 22 s between thefirst point Y0 and the second point P0 is assumed. A fourth point 36, atwhich the fourth line segment 35 intersects the third line segment 33,is assumed.

In order to form a substantial thickness between the side wall 21 e andthe spiral curve 22 s drawn by the inner peripheral wall of the swirlchamber 22, it suffices that the third point 34 be positioned on thethird line segment 33 on a side more distant from the center O_(22S) ofthe spiral (the center O₃₀ of the basic circle 30) than the fourth point36. In this respect, an extension (or possibly, the side wall 21 eitself) of the side wall 21 e of the swirl passage 21 does not intersectthe extension (or possibly, the spiral curve 22 s, namely, the innerperipheral wall surface itself) of the spiral curve 22 s, which is drawnby the inner peripheral wall of the swirl chamber 22, in an angularrange of more than 180 degrees rotated (orbited) from the starting pointSs of the spiral curve 22 s. That is, the extension of the side wall 21e of the swirl passage 21 connected to a downstream end side of theswirl chamber 22 does not intersect an extension of the swirl chamber 22on the downstream end side.

In the embodiment, the side wall 21 e is parallel to the side wall 21 s.As shown in FIG. 9, also in the case where a side wall 41 e is formed tomake a space between it and a side wall 41 s small as it goes toward adownstream side from an upstream side (taper off) and so a swirl chamber41 is formed to taper off, a third point 34, at which the side wall 41 eand a third line segment 33 intersect each other, may be arranged in themanner described above. In this case, however, since the side wall 41 eis provided to be oblique to the side wall 21 e, the extension of theside wall 21 e can be made not to intersect the extension of the spiralcurve 22 s in an angular range of more than 180 degrees rotated(orbited) from the starting point Ss of the spiral curve 22 s even whenthe third point 34 is positioned on the third line segment 33 on a sidetoward the center O_(22S) of the spiral curve (the center O₃₀ of thebasic circle 30) from the fourth point 36. In this case, it is importantthat the extension of the side wall 21 e is made not to intersect theextension of the spiral curve 22 s in an angular range of more than 180degrees rotated (orbited) from the starting point Ss of the spiral curve22 s.

Also, the side wall 21 e can be defined by a curve, in which case,likewise the swirl chamber 41 shown in FIG. 9, it is important that theextension of the side wall 21 e is made not to intersect the extensionof the spiral curve 22 s in an angular range of more than 180 degreesrotated (orbited) from the starting point Ss of the spiral curve 22 s.

The second point P0 defines a terminating end (terminating point) Se ofthe spiral curve 22 s drawn by the inner peripheral wall of the swirlchamber 22. Provided at Se is a circular-shaped portion 26 formed so asto come into contact with the spiral curve 22 s at the terminating pointSe. Since the circular-shaped portion 26 is formed over the whole of theswirl passage 21 and the swirl chamber 22 in a heightwise direction(direction along a swirl central axis), it constitutes a partialcylindrical-shaped portion formed in a predetermined angular range in acircumferential direction. The side wall 21 e of the swirl passage 21 isformed in a manner to come into contact with a cylindrical-shapedsurface defined by the circular-shaped portion 26 and the contact point37 defines a downstream end (terminating point) of the side wall 21 e ofthe swirl passage 21. The cylindrical-shaped surface defined by thecircular-shaped portion 26 constitutes a connecting surface(intermediate surface), which connects between the downstream end of theside wall 21 e of the swirl passage 21 and the terminating end Se of theinner peripheral wall of the swirl chamber 22.

Also, the terminating end (terminating point) Se of the spiral curve 22s drawn by the inner peripheral wall of the swirl chamber 22 and thedownstream end (terminating point) 37 of the side wall 21 e of the swirlpassage 21 are distant from each other to form a thickness φK. In thisembodiment, the length of a perpendicular line from the terminating end(terminating point) Se of the spiral curve 22 s to the extension of theside wall 21 e is made the thickness φK. In addition, the terminatingend (terminating point) Se of the spiral curve 22 s drawn by the innerperipheral wall of the swirl chamber 22 and the downstream end(terminating point) 37 of the side wall 21 e can be determined by achange in bend or curvature.

Also, the reason why “extension” is represented likewise “extension ofthe side wall 21 e” and “extension of the spiral curve 22 s” in theabove description is that according to the embodiment, the terminatingend Se of the spiral curve 22 s is positioned upstream of a point Y0 onthe spiral curve 22 s and its extension. For example, in the case wherethe terminating end Se of the spiral curve 22 s is made to agree withthe point Y0, “the side wall 21 e” and “the spiral curve 22 s” should bedescribed instead of “extension of the side wall 21 e” and “extension ofthe spiral curve 22 s”.

While the above assumption and the structure have been described withrespect to a spiral curve, they are also applicable to an involute curvewhen a spiral curve is replaced by the involute curve.

Also, the thickness forming portion 25 may be straight in cross sectionas shown by a line segment 38 in FIG. 8 instead of being partiallycircular. In this case, the thickness forming portion 25 is made aplane. It is preferable that the plane be formed as a surface inparallel to the Y-axis and perpendicular to the XY plane.

In addition, the thickness of the wall surfaces is formed to include anangle R and an angular chamfer (in the order of 0.005 mm), which arenecessary in working.

FIG. 6 is a view illustrating the symmetric property of spray relativeto the thickness φK of the thickness forming portion 25 and suggestingthat a predetermined thickness range is effective in order to meet atarget value.

The dimension of the thickness φK is allowed to range from about 0.01 mmto 0.1 mm and preferably adopts 0.02 mm to 0.06 mm with priority.

The thickness φK relaxes collision of a fuel orbiting in the swirlchamber 22 and a fuel inflowing from the swirl passage 21 to form asmooth flow along the spiral wall surface in the swirl chamber 22.

In addition, since the graph shown in FIG. 6 takes no consideration ofdislocation of the connection of the swirl chamber 22 and the swirlpassage 21, it results that a design target value is met even when thethickness φK of the thickness forming portion 25 is 0. It is seen fromthe graph of FIG. 6 that in order to meet the design target value, thereexists an upper limit for the thickness φK. Also, while the graph ofFIG. 6 shows the result of meeting the design target value even when thethickness φK is 0, this is because consideration is not taken ofdislocation of the connection of the swirl chamber 22 and the swirlpassage 21, and as described in “Background of the Invention”,dislocation of the connection of the swirl chamber 22 and the swirlpassage 21 is liable to generate in the case where the thickness φK isnot provided (in case of 0). Accordingly, in view of dislocation of theconnection in the case where the thickness φK is not provided, it ispossible that the design target value is not met.

FIGS. 10A and 10B show results of analysis of fuel flow. Arrow vectorsrepresent flows. FIG. 10A shows the case where the side wall 21 e of theswirl passage 21 and the inner peripheral wall of the swirl chamber 22intersect each other and an edge-shaped portion being sharp at the pointlike a knife edge is formed on the connection of the both walls. FIG.10B shows the case where the thickness forming portion 25 is formed onthe connection of the both walls.

Observing the flows shown in FIG. 10A, a fuel inflowing from the swirlpassage 22 assumes a flow configuration, in which it merges into flowsorbiting in the swirl chamber 21 and is pushed against a wall surfaceside of the swirl chamber 22 as shown by an arrow 51. In such case, afuel spray (liquid film) flowing out of the fuel injection port 23becomes asymmetric.

Observing the flows shown in FIG. 10B, collision of flows leaving thethickness φK of the connection and orbiting in the swirl chamber 22 andflows from the swirl passage 21 is relaxed and flows along the curvatureof the swirl chamber 22 are formed as indicated by an arrow 52. In suchcase, flows are formed substantially symmetrically in the fuel injectionport 23 and so fuel sprays injected from the fuel injection port 23 aremade symmetrical.

The embodiment described above provides the following structure, action,and effect together.

The fuel injection port 23 is substantially large in diameter. When thediameter is made large, a cavity formed inside can be made substantiallylarge. So-called swirl speed energy there can be made to act on thinfilm formation of an injected fuel without loss.

Also, since the ratio of an injection port diameter to a plate thickness(the same as the height of the swirl chamber in this case) of the fuelinjection port 23 is made small, loss in swirl speed energy is verysmall. Therefore, a fuel atomizing property becomes very excellent.

Further, since the ratio of an injection port diameter to a platethickness of the fuel injection port 23 is small, an improvement inpress-forming is achieved.

With such structure, restriction of dimensional dispersion owing to animprovement in workability, not to mention the cost reduction effect,achieves a marked improvement in spray configuration and robustness ofinjection quantity.

As described above, with the fuel injection valve according to theembodiment of the invention, the predetermined thickness forming portion25 is provided on the connection of the swirl chamber 22 and the swirlpassage 21, 41 to ensure the symmetric property of an injected fuel toform a uniformly thin film, thereby accelerating atomization.

Since the thickness forming portion 25 aligns the swirling flow of afuel, which orbits in the swirl chamber 22, in a direction of curvatureof the spiral wall surface 22 s, the fuel merges into a fuel, whichinflows from the swirl passage 21, 41, to be accelerated to flow in theswirl chamber 22. At this time, a great collision of a fuel orbiting inthe swirl chamber 22 and a fuel inflowing from the swirl passage 21 isavoided, so that the fuel orbiting in the swirl chamber 22 flows alongthe curved surface of the swirl chamber 22 while accelerating andinducing the fuel inflowing from the swirl passage 21.

Thereby, a symmetrical (uniform in a circumferential direction about aswirl central axis) liquid film made thin by an adequate swirl intensityis formed at the outlet of the fuel injection port 23 to enableaccelerating atomization.

The fuel spray made uniformly thin in this manner actively makes anenergy exchange with an ambient air to be accelerated in breakup to bemade a spray of good atomization.

Also, design dimensions, which facilitate press-forming, can make a fuelinjection valve excellent in cost performance and inexpensive.

While the embodiment has been described, it is apparent to those skilledin the art that the invention is not limited thereto but various changesand modifications may be made within the spirit of the invention and thescope as defined by the appended claims.

The invention claimed is:
 1. A fuel injection valve including: a swirlchamber having an inner peripheral wall formed to be gradually increasedin curvature toward a downstream side from an upstream side; a swirlpassage, through which a fuel is introduced into the swirl chamber; anda fuel injection port opened to the swirl chamber, wherein the swirlchamber and the swirl passage are formed so that a side wall of theswirl passage connected to a downstream end side of the swirl chamber,or an extension thereof is made not to intersect a downstream sideportion of the inner peripheral wall of the swirl chamber, or anextension thereof.
 2. The fuel injection valve according to claim 1,wherein assuming, respectively, a first straight line segment connectingbetween a center of the swirl chamber and a starting point of the innerperipheral wall of the swirl chamber on an upstream side, a first pointY0, at which the first line segment and an extension of the innerperipheral wall extended toward a downstream side intersect each other,a second straight line segment passing through the first point Y0 andbeing perpendicular to the first line segment, a second point P0, atwhich the second line segment intersects the inner peripheral wall or anextension thereof on an upstream side of the first point Y0, a thirdstraight line segment connecting between the second point P0 and thecenter of the swirl chamber, a third point, at which the side wall ofthe swirl passage and the third line segment intersect each other, afourth straight line segment being parallel to the second line segmentand in contact with the inner peripheral wall or an extension thereofbetween the first point and the second point, and a fourth point, atwhich the fourth line segment intersects the third line segment, thethird point is positioned on the third line segment on a side moredistant from the center of the swirl chamber than the fourth point. 3.The fuel injection valve according to claim 1, wherein the cross sectionof the swirl chamber is defined by an involute curve or a spiral curve.4. The fuel injection valve according to claim 1, wherein a thicknessforming portion is formed between a downstream end of the side wall ofthe swirl passage and a downstream end of the inner peripheral wall ofthe swirl chamber.
 5. The fuel injection valve according to claim 4,wherein the cross section of the thickness forming portion is defined bya circular-shaped portion.
 6. The fuel injection valve according toclaim 5, wherein the circular-shaped portion is formed to be in contactwith the inner peripheral wall and the side wall at the downstream endof the inner peripheral wall and the downstream end of the side wall. 7.A fuel injection valve including: a swirl chamber having an innerperipheral wall formed to be gradually increased in curvature toward adownstream side from an upstream side; a swirl passage, through which afuel is introduced into the swirl chamber; and a fuel injection portopened to the swirl chamber, wherein a thickness forming portion isformed between a downstream end of a side wall of the swirl passageconnected to a downstream end side of the swirl chamber and a downstreamend of the inner peripheral wall of the swirl chamber.
 8. The fuelinjection valve according to claim 7, wherein that cross section of thethickness forming portion, which is perpendicular to a valve axis, isdefined by a circular-shaped portion.
 9. The fuel injection valveaccording to claim 8, wherein the circular-shaped portion is formed tobe in contact with the inner peripheral wall and the side wall at thedownstream end of the inner peripheral wall and the downstream end ofthe side wall.